This invention relates generally to liquid sterilization systems and more particularly to apparatus and methods for pasteurizing milk and colostrum for feeding to calves.
Calves in dairy harvesting facilities are fed non-saleable (“waste”) milk collected from cows that have been removed from the main herd for medical or other reasons. While the feeding of non-saleable milk to dairy calves would seem to be economical for the dairy operator, there is a risk that infectious pathogens may be transmitted through the milk or shed directly from the cow's mammary gland. Other pathogens can be deposited in milk from manure or dirt, or can result from proliferation in milk that is not chilled or stored properly.
To reduce this risk, it is preferred that milk or colostrum be pasteurized before feeding to calves. Pasteurization in known processes includes heating milk to a target temperature to kill a target microbe and maintaining that temperature for a period of time. The pasteurized milk ordinance defines two different methods for pasteurization: 1) batch pasteurization at 145° F. for 30 minutes (low-temperature, long-time or LTLT), or 2) high-temperature, short-time pasteurization (HTST) at 161° F. for 15 seconds (usually using a continuous flow process). Heating and maintaining the heat above a target temperature results in a log reduction in concentration of viable bacteria. However, some heat-tolerant bacteria may survive the process. Further, in a poor quality milk with very high concentrations of bacteria, some pathogenic bacteria may survive the pasteurization process.
Pasteurization is desirable and sometimes necessary to kill bacteria, such as E. coli, B. Cereus, and salmonella that are harmful to calves. Heat pasteurization to 145° F. is successful at killing nearly 100% of these bacteria if the milk is maintained above 145° F. for at least thirty minutes. One study suggests that a lower temperature of 120° F. can be used, but that temperature must be maintained for at least sixty minutes.
Once pasteurized, milk may be bottled, chilled, stored, and then reheated to a feeding temperature of between 100° F. to 110° F. It may not be necessary to store pasteurized milk because it is more readily available and can be fed directly to calves after it is heat pasteurized and cooled to feeding temperature.
Also, colostrum is fed to newborn calves within two hours of birth and again within twelve hours of birth. Colostrum is collected from cows shortly after calving, and includes relatively high concentrations of carbohydrates, protein, and antibodies. Colostrum also contains high concentrations of immunoglobulins, such as IgG, and growth factors. Pasteurizing colostrum can result in congealing and loss of immunoglobulins. About 25% to 30% of IgG concentrations in colostrum are destroyed in heat pasteurization of colostrum and milk. Thus, heat pasteurization is beneficial overall, but has detrimental affects on milk and colostrum. Colostrum is usually chilled, bottled, and stored prior to re-heating and feeding.
Ultraviolet pasteurizers can also be used to treat milk. U.S. Pat. No. 6,916,452, to Rix et al. discloses that milk can be sterilized in a dairy using one or more UV sterilizer units while maintaining milk temperature above 82.4° F. (28° C.) before it is transferred to a chiller and a bulk milk storage vat. Such a pasteurizer is conceptually well-founded, but is not able to be used on its own in a dairy facility because it lacks critical features necessary to prepare the milk and colostrum for distribution and feeding to calves.
An improved pasteurization system is needed that successfully kills harmful bacteria, but destroys little or no immunoglobulins for optimum calf health.